Contact arrangement for a high-voltage power circuit breaker

ABSTRACT

A contact arrangement is disclosed for a high voltage power circuit breaker wherein compressed gas is blown through the arc developed when the breaker is switched. The contact arrangement includes at least two contact pieces having respective hollow interiors for accommodating the discharge of the gas blown through the arc. Arcing electrodes between which the arc is drawn when the breaker is switched to the open position are electrically and mechanically joined to the contact pieces respectively. Each arcing electrode and the corresponding contact piece conjointly define an interface whereat the arc electrode is joined to the electrode piece. An electrically conductive supplement is contained in the electrodes in the region thereof next to the interface. The supplement comprises at least one metal and the arcing electrodes are made of carbon bodies and have a nozzle-like configuration. With the contact arrangement of the invention, increased mechanical strength is imparted to the graphite electrode and large differences in conductivity at the interface are obviated.

United States Patent [1 1 Kessler et al.

[ Dec. 9, 1975 [5 CONTACT ARRANGEMENT FOR A HIGH-VOLTAGE POWER CIRCUIT BREAKER [75] Inventors: Claus Kessler; Helmut Beier, both of Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Munich,

Germany [22] Filed: Apr. 23, 1973 [21] Appl. No.: 353,365

[30] Foreign Application Priority Data Primary Examiner-Robert S. Macon Attorney, Agent, or Firm-Kenyon & Kenyon Reilly Carr & Chapin ABSTRACT A contact arrangement is disclosed for a high voltage power circuit breaker wherein compressed gas is blown through the are developed when the breaker is switched. The contact arrangement includes at least two contact pieces having respective hollow interiors for accommodating the discharge of the gas blown through the arc. Arcing electrodes between which the arc is drawn when the breaker is switched to the open position are electrically and mechanically joined to the contact pieces respectively. Each arcing electrode and the corresponding contact piece conjointly define an interface whereat the arc electrode is joined to the electrode piece. An electrically conductive supplement is contained in the electrodes in the region thereof next to the interface. The supplement comprises at least one metal and the arcing electrodes are made of carbon bodies and have a nozzle-like configuration. With the contact arrangement of the invention, increased mechanical strength is imparted to the graphite electrode and large differences in conductivity at the interface are obviated.

6 Claims, 3 Drawing Figures I US. Patent Dec. 9, 1975 SheetlofZ 3,925,631

k A 7/// r//,////////i U.S. Patent Dec. 9, 1975 Sheet 2 of2 3,925,631

Fig. 2

IIIIIIIIIIIA CONTACT ARRANGEMENT FOR A I HIGH-VOLTAGE POWER CIRCUIT BREAKER BACKGROUND OF THE INVENTION Deutsche Offenlegungsschrift 1,913,973 discloses an electric circuit breaker with a blasting arrangement having a piston and a cylinder. The disclosed circuit breaker also includes two stationary nozzle-shaped contacts between which anarc is drawn when the breaker opens under load. The contacts are made hollow to remove the switching gases produced during the interrupting operation. The arcing electrodes between which the arc is drawn consistof arc-resistant, electrically conductive material;

Materials used for the arc electrodes are silver-tungsten or copper-tungsten. The burn-off with these materials caused by the actionof the arc'is considerably less than with other metallic materials of high electrical conductivity. Also, Deutsche Auslegeschrift 1,154,548 discloses how the circuit breaker contacts which draw an arc during the interrupting action are fabricated of carbon and, especially, how the contacts aremade of graphite. In such circuitbreakers graphite contacts can be used to particular advantage if an electronegative, fluorine-containing gas especially such as sulfur hexafluoride (SP is used as thearc quenching and, if required, as the insulating medium. It has been determined that with the same arcing'load, the material loss of graphite contact pieces is substantially smaller than of metallic contact pieces, even if they consist of highquality, arc-resistant material such as silver-tungsten or copper-tungsten. This in turn has a favorable effect on the quality and quantity of the decomposition products generated under theaction of the arc.

In electric power circuit breakers with graphite electrodes, the difficulty occurs that the graphite bodies used as arcing electrodes must be connected mechanically and electrically with the current-carrying contact pieces consisting as a rule of copper. This presents the problem that graphite bodies usually have insufficient mechanical strength to allow a thread to be machined therein for making the connection with the contact piece. The further problem is presented that because the conductivity of the contact piece material is different from the .conductivity of the electrode material, a

discontinuity results at the interface where the conducting connection is formed; this condition has been shown to be disadvantageous in some cases.

BRIEF SUMMARY OF THE INVENTION It is an object of the invention to provide a contact arrangement wherein the discontinuity in conductivity between thecontact piece material and electrode is mitigated and wherein increased mechanical strength is imparted to the electrodes of the contact arrangement. It is another object of the invention to provide a contact arrangement wherein wear is minimized where the movable switching member contacts the electrode of a contact piece. 7

The contact arrangement according to the invention is utilized in high voltage power circuit breakers, especially those of the compressed gas type,-and is provided where the breaker is switched between open and closed positions. The contact arrangement includes asa feature at least two contact pieces having respective hollow interiors for accommodating the discharge of the gas blown through the arc. Arcing electrodes between which the arc is drawn when the breaker is switched to the open position are electrically and mechanically joined to respective ones of thecontact pieces. Each arcing electrode and the corresponding contact piece conjointly define an interface whereat the arcing electrode is joined'to the contact piece. The arcing electrodes are made from carbon bodies and have a nozzlelike configuration. An electrically conductive supplement is contained in each of the electrodes in the region thereof next to interface and the supplement comprises one or more metals.

The metallic supplements can be embedded in the graphite body, for example, by sintering and impart a comparably higher mechanical strength which makes it possible to stress the graphite body to a higher degree, for instance, where the electrode is joined to the contact piece. The metallic supplements effect an increase in the conductivity of the graphite body, and this is advantageousparticularly in an embodiment of the invention wherein the hollow contact pieces are arranged so as to be stationary and can be bridged by a bridging contact member which, in the course of the interrupting motion, slides over the arcing electrode of at least one of the stationary contact pieces.

Through the application of graphite bodies which are provided with an electrically conducting supplement of one or more .metals at the location. where electrical connection with the bridging contact member is made, the electric conductivity of the sliding surface of the electrodes can be matched to the conductivity of the contact pieces through an appropriate choice of the concentration of the added metals so that the influence of discontinuities is thereby decreased. It is particularly advantageous if the area of the arcing electrode over which the bridging contact member travels has the highest concentration of the added metal. The wear of the sliding surface of the electrodes, caused by the movement of the contact fingers of the bridging contact member is moreover, reduced or avoided by the metal addition. 1 1

In one advantageous embodiment of the invention, in which the bridging contact member is of tubular configuration and surrounds the stationary contact pieces, the outer surface of the graphite body is provided with the metal supplement. Such an embodiment is preferred particularly for electric power circuit breakers with a blasting arrangement consisting of a piston and a cylinder.

In still another embodiment wherein the bridging contact member is slideably' guided inside the hollow contacts, the inside surface of the graphite body is provided only in part with a metallic supplement. In such an embodiment of the contact arrangement, the arc is drawn in the course of the interrupting motion into the region of the interior of the contacts which has a beneficial effect on'the quenching conditions.

In all embodiments, wherein a mounting surface is provided for the graphite bodies on the contact pieces, the regions of the contact bodies at the mounting surfaces are advantageously determined for the metallicelectric connection with the contact pieces.

Although the invention is illustrated and described herein as a contact arrangement for a high-voltage circuit breaker, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram partially in section of thecontact arrangement according to the invention. The contact arrangement constitutes part of a highvoltage circuit breaker, especially one of thecompressed-gas type. The left half of the diagram shows the equipped with anauxiliary contact.

DESCRIPTION FOR PREFERRED EMBODIMENTS OF THE INVENTION The high-voltage power circuit breaker shown in FIG. 1 comprises a switching chamber 1 which can be of porcelain for example. In the interior 2 of the chamber 1, a gaseous insulating medium such as sulfur hexafluoride is under a pressure of bar for example. Inside the switching chamber 1 two contact pieces 3, 4 are arranged and carry respective arcing electrodes 5, 6 at their mutually adjacent end faces. The contact pieces 3, 4 are made hollow for the removal of switching gases whereas the arcing electrodes 5, 6 are graphite bodies of nozzle-shaped configuration. The hot switching gases generated during the arcing period are passed on through the nozzle-shaped graphite bodies 5, 6 into the interior of the hollow contact pieces 3, 4. On the left side of the center-line 7, the breaker is in the open position, and to the right of the center line 7, in the closed position. In the closed position, the two contact pieces 3, 4 are electrically connected witheach other by a bridging contact member 8. In the open position, the gap between the two contact pieces 3 and 4 is opened by the bridging contact member 8 which had been moved in the direction of the arrow 9. In the course of the movement of the bridging contact member 8 in the direction of the arrow 9, the gaseous quenching medium is conducted under a predetermined pressure, for example, 10 bar, to the gap and discharged from there through the hollow contact pieces 3 and 4.

FIG. 2 an enlarged view-of the arcing electrode 5 with its corresponding contact piece 3. The'bridging contact member 8 is shown in a position through which the member passes in the course of the interrupting motion. The graphitebody constituting the arcing electrode has an electrically conductive supplement 11 comprising of one or several metals; this supplement 11 is provided at the location 10 where the arcing electrode is electrically-mechanically connected with the contact piece 3. The metal supplement 11 increases the mechanical strength of the graphite electrode 5 to the extent that a sufficiently strong connection between the graphite electrode and the contact piece 3 is possible,

for example, a connection established by a threadwinding. In addition, the electrically conductive metallic supplement effects an increase of the electric conductivity of the graphite electrode primarily in the region of the outer surface 13 slideably engaged by the bridging contact member 8 during the interrupting motion of the contact fingers (not shown) of the bridging contact member is at the same time reduced or avoided.

In the position shown wherein the bridging contact member 8 is already electrically separated from the graphite body 5, an arc is drawn which is driven into the interior of the graphite body 5 under the influence of the gas stream which is building up. The footpoint of the arc travels across the surfaces 15 of the graphite body consisting preferably of pure graphite. The embodiment shown in FIGS. 1 and 2 has stationary contact pieces 3, 4 which can be bridged by a bridging contact member 8 which is preferably of tubular configuration and slides over the arcing electrode of at least one of the stationary contacts in the course of the interrupting motion. The bridging contact member 8 then surrounds the stationary contact pieces 3, 4 for which the outer surface region of the graphite bodies 5 and 6 are provided with the metal supplement.

In the alternate embodiments of the invention shown in FIG. 3, the bridging contact member 8 is provided with a tubular burn-off auxiliary contact 8a which is slideably guided in the interior 16 of the hollow contact pieces 3, 4. Such an auxiliary contact is described, for example, in the copending application Ser. No. 337,174, filed on Mar. 1, 1973 with the title: Compressed-Gas Circuit Breaker. The inner surface of the graphite bodies 5,6 is provided in part with a metal supplement. The mounting portions 17 provided at the contact pieces 3 and 4 for the respective graphite bodies 5, 6 also have a metal supplement which in addition to being advantageous for the mechanical connection, is advantageous for the electric-metallic connection with the contact pieces.

Typical of metals used as the metal supplements are copper, silver and alloys with copper orsilver.

What is claimed is:

1. In a high-voltage, compressed gas power circuit breaker wherein the gas is blown through the arc developed when the breaker is switched, a contact arrangement whereat the circuit breaker is switched between open and closed positions, the contact arrangement comprising at least two metal contact pieces having respective hollow interiors for accommodating the discharge of the gas blown through the arc, arcing electrodes between which the arc is drawn when the breaker is switched to the open position, said contact pieces being mounted in the breaker so as to conjointly define a gap therebetween, and a bridging contact member movable relative to said contact pieces between open and closed positions to electrically join said contact pieces in the closed position and to electrically separate said contact pieces in the open position whereby the arc is drawn when said gap is'opened, said bridging contact member being arranged with respect to said contact pieces so as to cause said bridging contact member to slide over the electrode of at least one of said contact pieces when moving into said open position from said closed position, said arcing electrodes being electrically and mechanically joined to said contact pieces respectively, each of said arcing electrodes and the corresponding contact piece conjointly defining an interface whereat the arcing electrode is joined to the contact piece, said arcing electrodes being made from carbon bodies and having a nozzle-like configuration, and an electrically conductive supplement embedded in each of said electrodes in the region thereof next to said interface to increase the conductivity of said carbon electrode at said region to mitigate the discontinuity in conductivity between said carbon electrode and said metal contact piece at the joint therebetween and to also impart an increased tioned region greater than the concentration thereof at the first mentioned region of the same electrode.

4. The contact arrangement of claim 2, said bridging contact member having a tubular configuration and being arranged in surrounding relation to the contact pieces, said region of said electrodes containing the metal supplement extending to the outer surface of the electrode.

5. The contact arrangement of claim 2, said electrodes having respective inner "surfaces, said bridging contact member being guided in the hollow interiors of said contact pieces so as to slideably contact said inner surfaces of said electrodes, and additional quantities of the metal supplement being contained in only a portion of said inner surfaces of said electrodes.

6. The contact arrangement of claim 2, said contact pieces having respective mounting surfaces for receiving said arcing electrodes thereon, said contact pieces also containing quantities of said supplement in the regions thereof at said mounting surfaces. 

1. IN A HIGH-VOLTAGE, COMPRESSED GAS POWER CIRCUIT BREAKER WHEREIN THE GAS IS BLOWN THROUGH THE ARC DEVELOPED WHEN THE BREAKER IS SWITCHED, A CONTACT ARRANGEMENT WHEREAT THE CIRCUIT BREAKER IS SWITCHED BETWEEN OPEN AND CLOSED POSITIONS, THE CONTACT ARRANGEMENT COMPRISING AT LEAST TWO METAL CONTACT PIECES HAVING RESPECTIVE HOLLOW INTERIORS FOR ACCOMODATING THE DISCHARGE OF THE GAS BLOWN THROUGH THE ARC, ARCING ELETRODES BETWEEN WHICH THE ARC IS DRAWN WHEN THE BREAKER IS SWITCHED TO THE OPEN POSITION, SAID CONTACT PIECE BEING MOUNTED IN THE BREAKER SO AS TO CONJOINTLY DEFINE A GAP THEREBETWEEN, AND A BRIDGING CONTACT MEMBER MOVABLE RELATIVE TO SAID CONTACT PIECES BETWEEN OPEN AND CLOSED POSITION TO ELECTIRCALLY JOIN SAID CONTACT PIECES IN THE CLOSED POSITION AND TO ELECTRICALLY SEPARATE SAID CONTACT PIECES IN THE OPEN POSITION WHEREBY THE ARC IS DRAWN WHEN SAID GAP IS OPENED, SAID BRIDGING CONTACT MEMBER BEING ARRANGED WITH RESPECT TO SAID CONTACT PIECES SO AS TO CAUSE SAID BRIDGING CONTACTS MEMBERS TO SLIDE OVER THE ELECTRODE OF AT LEAST ONE OF SAID CONTACT PIECES WHEN MOVING INTO SAID OPEN POSITION FROM SAID CLOSED POSITION, SAID ARCING ELECTRODES BEING ELECTRICALLY AND MECHANICALLY JOINED TO SAID CONTACT PIECES RESPECTIVELY, EACH OF SAID ARCING ELECTRODES AND THE CORRESPONDING CONTACT PIECE CONJOINTLY DEFINING AN INTERFACE WHEREAT THE ARCING ELECTRODE IS JOINED TO THE CONTACT PIECE, SAID ARCING ELECTRODES BEING MADE FROM CARBON BODIES AND HAVING A NOZZLE-LIKE CONFIGURATION, AND AN ELECTRICALLY CONDUCTIVE SUPPLEMENT EMBEDDED IN EACH OF SAID ELECTRODES IN THE REGION THEREOF NEXT TO SAID INTERFACE TO INCREASE THE CONDUCTIVITY OF SAID CARBON ELECTRODE AT SAID REGION TO MITIGATE THE DISCONTINUITY IN CONDUCTIVITY BETWEEN SAID CARBON ELECTRODE AND SAID METAL CONTACT PIECE AT THE JOINT THEREBETWEEN AND TO ALSO IMPART CONTACT PIECE AT THE JOINT STRENGTH TO SAID ELECTRODE AT SAID REGION TO INCREASE THE STRENGTH OF SAID JOINT, SAID SUPPLEMENT COMPRISING ST LEAST ONE METAL.
 2. The contact arrangement of claim 1, said contact pieces being fixedly mounted in the breaker.
 3. ThE contact arrangement of claim 2, said supplement being contained also in the region of the electrode corresponding to said one contact piece whereat said bridging contact member makes sliding contact therewith when moving into said open position, said supplement having a concentration in said last-mentioned region greater than the concentration thereof at the first-mentioned region of the same electrode.
 4. The contact arrangement of claim 2, said bridging contact member having a tubular configuration and being arranged in surrounding relation to the contact pieces, said region of said electrodes containing the metal supplement extending to the outer surface of the electrode.
 5. The contact arrangement of claim 2, said electrodes having respective inner surfaces, said bridging contact member being guided in the hollow interiors of said contact pieces so as to slideably contact said inner surfaces of said electrodes, and additional quantities of the metal supplement being contained in only a portion of said inner surfaces of said electrodes.
 6. The contact arrangement of claim 2, said contact pieces having respective mounting surfaces for receiving said arcing electrodes thereon, said contact pieces also containing quantities of said supplement in the regions thereof at said mounting surfaces. 